This project will study cellular and molecular mechanisms of immunodeficiency in acquired immunodeficiency syndrome (AIDS) which account for AIDS susceptibility to opportunistic infection with M. avium. It will use in vitro and in vivo models of antimycobacterial immunity in mice, and in vitro models using human peripheral blood and alveolar cells. Human cells will be obtained from healthy subjects who are PPD-negative or positive to PPD or PPD-Battey, from patients with M. avium infection with or without AIDS, and from AIDS patients without M. avium infection. The project will develop and characterize mouse in vitro and in vivo, and human in vitro cell models of M. avium infection and immunity, study the relative susceptibilities of mouse and human macrophages from different anatomical sites to infection with M. avium, analyse immune lymphokine production and its anti-avium effects in macrophages, and look for factors that may actively impair anti-avium immunity such as the recently discovered mycobacterial growth-enhancing cytokine.